High purity gas delivery systems, such as those used in semiconductor manufacturing or other thin film coating processes, typically include a source of high purity gas coupled through a series of gas distribution and control components such as a mass flow controller, one or more pressure sensors and/or regulators, a heater, one or more filters or purifiers, and shutoff valves. In semiconductor processing, a series-connected set of such components is usually referred to as a "gas stick". The components used and their particular arrangement in a gas stick can vary depending upon their design and application, with many component arrangements being known in the art. In a typical semiconductor processing arrangement, multiple gas sources are connected to the chamber through multiple gas sticks, which are typically mounted to a frame, forming a complete system known as "gas box". See, for example, U.S. Pat. Nos. 5,662,143; 5,819,782 and 5,863,023.
As the dimensions of semiconductor devices decrease and their densities increase, semiconductor manufacturing processes have become increasingly intolerant of particulate contamination. One important source of such contamination is the gases used during the process, and particularly particulates carried by the wetted surfaces in the passageways through the components and those connecting the components of the gas stick which delivers gas from the source to the chamber. Moisture or dust which accumulates within a gas stick or component will be carried with the source gas and deposit onto the semiconductor devices being processed, creating defects. Moisture also may corrode the wetted surfaces, leading to flaking of particles from these surfaces.
To reduce contamination of this sort, gas sticks and other gas processing components used in manufacturing semiconductor devices are usually made in low-dust, low-moisture environments, and purged for lengthy periods of time at elevated pressures after manufacture. The components are then typically packaged and sealed in pressurized nitrogen for shipment. As a result, the interior of the component or stick is exposed only to the clean room environment in which the semiconductor processing equipment is located, and only for the brief period of time between removal of the packaging and sealing of the stick or component into the processing equipment.
In addition, the gas processing components in a gas stick, and other components and connections in the gas distribution system, will wear and need replacement at various times throughout the life of the assembly of equipment. Typically, a component is replaced by closing the valves most nearly adjacent to the component, uncoupling and replacing the component, and reopening the adjacent valves. To simplify this operation and minimize the extent of the gas stick exposed to room air during this procedure, each component is typically connected to its neighboring components or tubing with removable couplers, and valves are placed between components at several locations along the stick. This tubing and the removable couplers can often be the source of leaks, and require careful attachment and detachment when repairing and/or replacing component parts. Further, the act of uncoupling a component or portion of the stick and removing it from the stick exposes that component and the replacement component to ambient conditions, and also exposes substantial wetted surface between the component and the nearest valves (including the inside of any connecting tubing, and potentially other components), to ambient conditions. Thus, the gas stick must be extensively purged when the components are reassembled.
One approach to eliminating connection parts, such as tubing and couplers, and facilitating maintenance of the components of the gas stick is to "down mount" the components on multiple fixing blocks, as shown, for example, in U.S. Pat. No. 5,819,782 (Itafuji). However, each component of a gas stick typically comprises highly machined parts and expensive electrical circuitry, making each component relatively expensive to manufacture and replace. When a component fails, the entire component is replaced even though in most instances the failure is mechanical (and in the case of a mass flow sensor, it is the sensor that usually fails). Each component is typically constructed with a mounting block, which in turn is made with multiple machine operations, making the component expensive. Thus, while down mounting the component parts on multiple fixing blocks solves one problem, it still is relatively expensive to replace defective parts.